It can be worrisome if your tree unexpectedly starts oozing sap. Failing to identify the reason can potentially result in larger problems in the future.
Why is my tree oozing sap? The most likely reason that your tree is oozing sap is that it’s infected with some sort of parasite. While often not serious, there are many ways of dealing with these infections. Damage from pruning and environmental stresses can also cause trees to leak sap.
Oozing sap is likely not a death sentence for your tree, but it is a sign that something is wrong. By correctly identifying the problem, you can be well on your way to resolving the issue and strengthening your tree.
Potential Reasons for a Tree Oozing Sap
There are many reasons why your tree can ooze sap. The most common reasons are infections by some sort of bacteria or parasite. While most infections are not serious, there are many ways to determine the reason behind your tree oozing sap.
1. Bacterial Wetwood (Slime Flux)
Bacterial wetwood is an infection of one or many species of bacteria. It affects trees by infecting deep within the tree and creating pressure.
When that pressure builds, it creates cracks in the tree from which to escape, and with the cracks comes sap from the inside of the tree.
If you’re trying to determine if your tree has bacterial wetwood, first determine if the tree is one of the more susceptible species. Below is a list of trees that are most likely to be attacked by bacterial wetwood:
- Elms
- Apple
- Crabapple
- London Plane
- Redbud
- Aspen
- Dogwood
- Magnolia
- Russian olive
- Beech
- Fir
- Maple
- Sour gum
- Birches
- Hemlock
- Mountain ash
- Sycamore
- Boxelder
- Hickory
- Mulberry
- Sweet Gum
- Butternut
- Horse Chestnut
- Oaks
- Tulip Tree
- Cottonwood
- Linden
- Pines
- Black Locust
- Poplar
- Willow
- Walnut
If you notice one of these trees oozing sap through fissures in the tree and the sap is killing grass below it, it’s likely bacterial wetwood.
2. Cytospora Canker (Gummosis)
Gummosis most commonly affects stone fruit trees (trees that produce fruit with pits, such as peaches, cherries, plums, etc.). While it is not serious, many factors cause gummosis that should be investigated.
If you notice your stone fruit trees oozing this gelatin-like gum in the spring, then it’s likely gummosis. Below are some common causes.
Poor Growing Conditions
The most common condition to cause gummosis is compacted soil. This often causes a clear ooze to come from the tree. One of the best solutions for this is to place plants nearby with deep taproots to help aerate the soil.
Borers or Diseases
Insect and disease infections often produce a milky or dark-colored sap known as biotic gummosis. Treat the infection, and the gummosis should resolve on its own.
Wounding
Wounding is another clear gummosis producer. If you’ve trimmed a branch or your tree has been damaged by a recent storm, it’s likely that gummosis will occur. Be careful to observe the wound since this is an easy way for a tree to become infected.
3. Pruning Wounds/Cuts
Most trees will ooze sap when they’re pruned. Make sure to use clean tools when you trim limbs from your trees to prevent bacterial infection. It may also be wise to use a pruning sealer in order to prevent any infection from setting in after you’ve opened a cut in your tree.
4. Pests Invading the Fruit, Shoots, or Trunk
One of the most common issues to impact any tree is the presence of parasitic insects. The most effective way to prevent tree pests is to have a strong, healthy tree that hasn’t been impacted by any environmental factors such as drought, sunscald, or injury.
Below is a list of common parasitic insects:
Borers
The most common borers are beetles in their larval stage. These insects often attack a tree through open wounds, such as pruning wounds, and feed on the tree by boring into it.
If not treated, borers can kill a tree. If your tree is already infected, the most common method of treatment is to use an insecticide.
Aphids
Aphids are tiny insects that often feed on the delicate parts of trees and plants. They are often not damaging, although they can impact the overall health of a tree if their numbers are large.
A great, natural way to deal with aphids is to introduce ladybugs into the area. A ladybug’s diet consists largely of aphids.
Oriental Fruit Moths
Oriental fruit moths are most attracted to peach trees and other stone fruit trees and feed exclusively on the fruit. They can be extremely damaging to peaches and destroy an entire crop before it has the chance to ripen.
The oriental fruit moth will damage the shoots of these trees by attacking the newly grown shoots. While the main damage occurs to the fruit, the moth can cause trees to look bushy because of the dead and flagging leaves.
The most common methods of combating these parasites are commercial pesticides and introducing braconid wasps (which are a parasite to the moth larvae).
5. Environmental Damage/Stress
Trees are also prone to ooze sap if they’ve been subjected to environmental damage. Drought, compacted soil, hot and dry summers, frost cracks, and sunscald caused by drastic temperature swings can all cause a tree to produce sap.
This is the root cause of many of the above issues, and treating it will often resolve the problem.
Can Bacterial Wetwood Kill Trees?
Bacterial wetwood is normally not a serious disease, but it can cause a tree to lose some of its vigor over time. A loss of vigor is characterized by stunted growth, a less vivid color, lower leaf quantity, or branch dieback in the upper crown of the tree.
Do Some Trees Naturally Drip More Sap Than Others?
Some trees are bigger sap producers than others. Maples are an obvious one since their sap is used to make maple syrup. Here is a list of some of the highest sap-producing trees:
- Maples
- Elms
- Birches
- Honey locusts
How To Prevent Excessive Tree Sap
The single best way to prevent trees from producing excessive sap is to treat the common causes before they become a problem.
- Make sure the environment for the trees is ideal and the tree is not becoming stressed. A stressed tree is much more susceptible to damage from pests than a stressed tree.
- Prune at the appropriate time and care for the pruning wound.
- Plant trees that resist the pests that would otherwise bore into the tree and cause a wound that would produce sap.
Related Questions:
Is Bacterial Wetwood (Slime Flux) Harmful to Humans?
While bacterial wetwood is damaging to any grass or other plant life that it lands on, it is not known to be harmful to humans or animals.
What Is the Difference Between Tree Sap and Tree Resin?
Sap and resin are often both referred to as sap, but they’re not the same. Sap is often a clear, watery, sugary substance while resin is an amber-colored, thick, and sticky fluid.
Conclusion
If your tree is oozing sap, it’s most often not a major concern, but it is wise to identify the reason behind it. When a tree bleeds sap, there’s almost always a reason, and that reason is almost always some sort of trauma to the tree that can be resolved with care.